1. Field of the Invention
The invention relates to cameras that use electronic flash devices, and more particularly, to flash-photography cameras capable of extended-time-interval photography, in which the photographer arbitrarily can select exposure time.
2. Description of Related Art
A known camera contains an internally housed strobe and can detect automatically when a subject is inadequately exposed. This camera sets a strobe automatic flash mode that causes the strobe to flash automatically, as needed. With this type of camera, a selection operation device, such as a selection button, allows switching between the automatic flash mode and an automatic flash prevention mode, which prevents automatic flash of the strobe. When the automatic flash prevention mode is selected, a forced flash mode also can be selected to flash the strobe forcibly, according to the desires of the photographer.
With this camera, however, the photographer arbitrarily uses the selection operation device to set the automatic flash mode, the automatic flash prevention mode or the forced flash mode. Depending on the photograph exposure mode of the camera, this operation can be troublesome or difficult, possibly allowing photograph opportunities to be missed.
For instance, when a night scene is being photographed, the bulb mode (B mode) typically is selected as the photograph exposure mode. In the B mode, film exposure continues for as long as the shutter release button is depressed, and the exposure is completed by removing the photographer's hand from the button. When a photograph is taken in the B mode, the automatic flash prevention mode generally is used.
Even when the B mode is selected, there are times, depending on the condition of the subject and the desires of the photographer, when the strobe should be either flashed for better photographic results--either only once during exposure, such as at the instant that the shutter release is operated, or repeatedly at specified time intervals during the exposure. In such cases, however, forced flash of the strobe cannot be achieved simply and arbitrarily, because the selection operation device must be operated to select the forced flash mode. This process is troublesome and difficult, making quick reaction to photograph opportunities impossible. Additionally, because a proper number of strobe flashes, either once at the time of shutter release or numerous times at set intervals, also must be determined, it is difficult to flash the strobe according to the desires of the photographer during extended exposure in the B mode.
With more recent cameras, a so-called time mode (T mode) has been proposed, in which exposure begins by operating the shutter release button, and ends, after a desired time interval, by again-operating the shutter release button or some other button. The T mode is effective when photographing night scenes, for example, or when taking underwater photographs of fish or similar objects. But when the T mode is used, it is difficult to flash the strobe selectively as needed, as with the B mode described above. A way to achieve strobe flash control with the T mode has not been devised.